Fuel burner control system



` Feb. 18, 1941. E. 1. HAEDIKE;

FUEL BURNER CONTROL SYSTEM Filed March 1, 1939 l v 5 43 T012/ 'Patented Feb. 18, .1941,

UNITED STATES'.

. 4 2,232,385 y FUEL nonnen connor. sysrm Edward J. Haedike, Chicago, lll., signor to National Machine Works, Chicago, Ill., a corpora-- tion of Iliinois Application March l, 1939, Serial No. 259,101

y 3 Claims. The invention relates to fuel burner control systems and more particularly to control sys-.-

tems for fuel burners provided with auxiliary or pilot burners of the on-oif-type. It will be un- 5 derstood that so-called on-oif pilot burners do not burn continuously, but are lighted only when used for igniting the main burner and are usually maintained lighted during the operation of the main burner. During the intervals in which l the main burner is of! the pilot burner is also off, Obviously, a saving in 'fuel is accomplished when using such an on-off pilot burner asvdistinguished from a pilot burner which is maintained in operation at all times, irrespective of l -the operation of the main burner. Furthermore, with the controlsys'tem herein disclosed, there is an obviation of a hazard sometimes occurring with constantly burning pilots. In particular, the supposedly constantly burning pilot may go out and danger then arises-when fuel is supplied to the main burner. With an on-oif pilot, however, the'ignition cycle for the pilot is re- ,peatedv before fuel is supplied tothe main burner so that there is positive insurance of a pilot 25 iiarn to light the main burner when the latter is turned on. y

One object o f the present invention is to provide a new and improved control system for a fuel burner with an on-oif type of pilot burner, in whichthe supply of fuel to themain burner cannot, under any circumstances be reinitiated after the pilot burner' has been shut olf, except l after a complete repetition of a predetermined pilot ignition cycle.

35 vA further object of the invention is to provide an electrical control system for a fuel burner with an on-o type of pilot burner, which sys-xv tem is of such 'character as to insure positively a sequential operation of the ignition mechanism 40 for the pilot burner and the fuel supply means for the main burner. I t

Another object of the invention is to-provide in a control system for a fuel burner with anon I 5 5 which said heater is governed by an improved and simplified circuit interconnected with the controls of the main andI pilot burners.

Further -obiects and advantages of the invention will becomeapparent'as thee following description proceeds, taken in connection with the 5 accompanying drawing in which:

Figure 1` is a wiring diagram and diagrammat iclayout of afuel burner control system embodying the present invention.

Figs. 2 and 3 are wiring diagrams similar to 10 Fig. l of two'mdified forms of' control systems embodying'the-'invention. I v l For purposes of illustration and explanation of its various novel features, the invention has been exemplified herein (Fig. l) in a control system l5 suitable for a main gas burner (not shown) supplled'with fuel through a main gas line i0. It will be appreciated that the invention is also applicable to control systems for other types offuel burners. i

In brief, the combustion mechanism includes, in addition to the main burner. a pilot burner il and a blower (not shown), driven by an electric motor I2, for supplying air for combustion y at the burners. Gas is supplied to the pilot v2li burner Il through a branch conduit I3 on the main supply conduit lll. Separate shut-ofi? valves Hand Al5 serve, respectively, to control thel flow of fuel to the main and pilot burners, these vvalves being actuated in a manner which will hereinafter appear. The general control of the system is'accomplished by means of-a main thermostat I6, 'which may be of the conventional blmetallic double-contact type as shown, or` of any other suitable form. The term fmain thermostat as used herein designates a thermostat or similar thermal responsive device actuated in accordance with'the temperature of the air or other medium in a space, such asa room, which is heatedveither directly or indirectlyfrom the main burner. v Generally stated, theassociated control system is adapted, under normal conditions, `to operate' the combustion apparatus in the following cycle. When the main thermostat i6 calls for heat, fuel 45 is supplied to the pilot burner Il and an ignition device is set in-operation to ignite the fuel at the pilot burner. Preferably, 'the fuel supply means for the pilot burner is interlocked with the blower. motor l2' so thatfuel will not be supplied to the 50 pilot burner until both the main and pilot burners .are conditioned for proper combustion by having the blower operating at or above a predetermined minimum speed. In' response to a successful ignition of the pilotburner Il .the l5 I fio pilot burner I I is a thermally actuated name devalve I4 is opened so as to supply fuel to the main burner. This supply of fuel to the main burner continues until the temperature at the main thermostat i6 is raised to a predetermined point at which time both the main and pilot burners are again shut down. Preferably a heat-anticipation heater is associated with the main thermostat, fas will hereinafter appear, to accelerate its point of opening. This cycle is repeated intermittently with such frequency as may be required to maintain the main thermostat within a predetermined temperature range.

Before proceeding with a description of the interrelation of the control system elements, the various parts will be identified. In the particular arrangement shown in Fig. 1, the control appa.-

4ratus includes a pilot ignition device, shown as an electrical resistancev heater coil Il, which in the actual construction is located closely ade jacent the pilot burner I I. lTo interlock the pilot y burner supply valve l5 with the blower motor |2,

a valve of the centrifugal type is used and is mechanically coupled with the blower motor I2 s0 that the valve I5 will be open only when. the motor I2 is operating at or above a predetermined minimum speed. Also associated with the tector shown as a thermocouple I8, connected in circuit withan energizing winding I9 of an as sociated relay designated -generally by the numeral 20.v This relay is provided with a pair of normally open contacts 2 l which are closed upon Y energizatlon of the actuating winding'lil.

'As to the main burner shut-oft valve Il, an actuating solenoid 22 is provided for this valve. When energized, the solenoid 22 serves to open the valve Il, this valve being normally biased to closed position. Current for actuating both the L pilot ignition coil Il, and valve actuator solenoid 22, -is supplied under the control of a main relay 23, as well as a two-position switching device designated generally by the numeral 2,4. The interconnection of thisrelay and switching device with the thermally controlled relay 23 will hereinafter appear'. The main relay 23 embodies an actuating winding 25, as well as normally open high and low voltage contacts 26 and'ZJ, respectively. similarly, the switching device u has been-shown as being a double-pole double-throw relayembodyinganactuatingwinding 23 aswell as two sets of double-throw contacts 23 and 3l with cooperating Y ilxed .contacts 23e-2lb and 30e-3B, respectively. The contacts 23* and 3l* are normally closed; that is, when the actuating winding 23 is deenerglzed.

Current for the system may be supplied, for example, from suitable alternating current sup- La -La for the low voltage portions of the control circuit.A In connection with the current supply arrangement,` it should also be noted. that the 'system preferablyv includes a step-down transformer 34 having a'primary winding 35 and a secondary winding'as. As'win hereinafter appear in greater detail, thisv transformer serves to supply current alternatively to the pilot ignition recoll'gi'lor to the burnervalve vactuating solenoid 22.

lInitiation of the normal cycle of operation is accomplished by closure of contacts 31 and 33 on the main thermostat I6. As the ambient temperature at this thermostat falls to a selected minimum value, the thermostat blade warps (to the left as shown in Fig. 1) and closes both the contacts 3l and 38. The lower contact 38 actually closes first but this sequential type of closure, for the moment, has no eect upon the system. Closure of the two -contacts 3l and 38 energizes the main relay actuating winding 25 (through a. circuit 1.3-25-39-29a-29-31- I6-38-40-L4). It will be understood that the primary winding 3l of .the main. transformer 32 is connected across the high voltage supply lines LiL-L2 at all times so that thesecondary winding 33 of this transformer is also energized at all times to provide a suitable low voltage across the supply lines Lee-L4.

Actuation of the main relay 23 causes it to close its two sets of contacts 26 and 2l. Closure of the contacts 21 completes an alternativeenergizing circuit for the main relay winding 25,

:through a heat-anticipation heater coil 4l associated with the main thermostat I6, but little or no'current flows through this coil for the moment since it is in shunt with the lower resistance energizing circuit forv the relay winding which was set forth-above. Closure of the other set of main relay contacts 26, however, connects the blower motor l2 across lthe high voltage 'sup-- coil Il,

From the foregoing, it will be seen that the rst burner I I, is initiated in response to energization of the main relay 23 by closure of 'the main thermostat contacts 31-38. To summarize, the energization` of the main relay 23 causes current to be supplied to the pilot burner ignition coil 1H as described above. Furthermore, tthe main blower motor yI2 is also started as described and when it actually reaches Vits proper operating speed the centrifugally actuated valve I5 is opened so as to permit gas to flow rthrough the supply conduit -l3 to the pilot burner l-I.

The second step 'in the cycle at operation, namely, the supply of fuel tothe main burner, by opening of the associated valve vll, is initiated in Vresponse 'to a successful ignition of the pilot burner II. When the flame at the pilot burner I I is burning properly, it heats the thermocouple Il so that the associated relay 2l closes its contacts 2l.' Closure of 'these contacts serves to energize the actuating winding 28 of the double.- pole, double-throw relay 2| (through a circuit Energlzation of Vthis -step in the cycle, namely, lighting of the pilot latter relay, or switching device, serves to shift 1 both of its double-throw contacts 23 and 30 to their upper 'positions (as viewed in Fig. 1) so that contacts 23-231 and 30-30 are closed.

Closure of the contacts 29-23" interrupts the previous energizing circuit xfor the main relay winding .25 and completes an alternative one through the relays own contacts 21. Shifting of the main relay energization to a non-pick-up or holding circuit is done for a. purpose which will hereinafter appear. Closure of the other set 'oi contacts 3040? servesrto energize .the main burner valve solenoid 22 and to interrupt .the energizing circuit for- 'the'pilot ignition coil Cil . supply circuit from which the pilotburner con-- 'connected in series with a thermocouple I8, asso-v tions falling within the spirit and scope of the invention.

I claim as my invention:V

1. In a control system for a main fuel burner having an on-oil' pilot burner, the combination of an electrically energizable ignition device for the pilot burner; electrically operated fuel control devices for the main and pilot burners; means including a main relay for controlling an electric trol device is energized to admit fuel to the pilot burner, saidmain relay having an initial energizing circuitand a separate non-pick-up holding circuit; a two-position switching mechanism operable in one position to complete a supply circuit from said rst named supply circuit controlled by said main relay, to said pilot ignition device: and operable in the other position to complete ka supply circuit from said nrst named supply circuit to said main burner fuel control device, said switching mechanism also being operable only in said one position to complete said initial enercircuit for said main relay and operable in said other position to interrupt said initial energizing circuit and to complete said relay holding circuit; and a main thermostat operable in one position to condition said relay energizing circuit for completion by said switching mechanism and in itsother position to interruptsaid holding circuit, said switching mechanism being normally urged to said other position, and means forv actuating said switching mechanism to said 4 one position in response to pilot ignition.

2. In a control system for a main fuel burner having an on-oif pilot burner, the combination of a main thermostat provided with rst and second setsof contacts arrangedto be opened sequentially in the order named .as the thermostat is heated, a heat-anticipation electric heater associated with said thermostat, electrically cn-` ergizable ignition and fuel supply control devices for the pikt andmain burners respectively, means including a main relay for controllingan -electric supply circuit from which the pilot burner control device is energized to admit fuel to the pilot burner, saidmain relay having an initial energizing circuit controlled by both of said sets of contacts and a separate non-pick-up holding circuit, a two-position switchy mechanism operable-in one position to complete a supply circuit from said rst named supply circuit to said pilot ignition device and operable in the other position to complete a supply circuit from said nrst named supply circuit to. said main burner fuel control device, said switching mechanism also being operable vonly in saidone position to complete said initial energizing circuit for said main relay and operable in said other position to interrupt said initial energizing circuit and to complete said holding circuit therefor, said holding circuit embodying two parallel connected branches with said heater included in one branch and said iirst set of contacts included in the other branch, said switching mechanism being normally urged to saidother position, and means for actuating said switching mechanism to said one position in response to pilot ignition.

3. In a control system-for a main fuel 4burner having an on-oif pilot burner, the combination of y t a. main thermostat provided with rst and second sets of contacts arranged to be opened sequentia/lly in the order named as the-,thermostat is heated, a'heat-anticipation electric heater asso-v ciated with said thermostat, electrically energizable ignition and fuel control devices for the pilot and main burners respectively, a first switching means operable alternatively to connect said ignition ,devicel and said main burner fuel control device to a source of lcurrent for actuation of the same, said rst switching means being normally urged to a position for connecting said ignition device to said source of current, means operable in response to ignition of the pilot burner for shifting said iirst switching means toits alternate i position to connect said main fuel burner control device to said source of current, a second switching means operable when shifted from a first position to a second position to disable both'v said ignition and pilot burner fuel control devices, electromagneticmeans for operating said second `switching means and operable when energized to retain said second switching means in'snid second position, and an energizing circuit for said electromagnetic means including apair of parallel connected branches connected in serie witha common portion of the circuit, said first set-of Y thermostat contacts being interposed in said common portion, said second set it-contacts in one of said parallel branches', and said electric heater inthe other branch. Y EDWARD J. -HAE'DIKE 

